1. Field of the Invention
The present invention relates to an ophthalmic apparatus for photographing the anterior part of an examinee's eye, particularly to an ophthalmic photographing apparatus comprising a device capable of photographing sectional images of the anterior part of the eye with a reproducible photographing position.
2. Description of Related Art
Conventionally, there are some kinds of ophthalmic photographing apparatuses which project a slit light to the examinee's eye, and photograph a sectional image of the anterior part of the eye on the basis of Scheimpflug's principle. Picture images of the eye obtained through the conventional apparatuses are analyzed to provide useful data including inclination and decentration of the IOL (Intra Ocular Lens). For analysis to find the inclination and decentration of the IOL and for another analysis, for instance Densitometry and Biometry, it is useful to reproduce the photographing position in order to detect the progressing variation in the data.
To align a conventional photographing optical system to an examinee's eye, a reticle of the photographing optical system is adjusted to Purkinje images focused on the cornea of the examinee's eye, particularly the first Purkinje image on the anterior surface of the cornea, by the hand of an operator with experience.
However, in the above conventional alignment operation, depending on the experience of the operator, the quality of photographed picture images will differ from operator to operator. Even same operator can not execute closely the alignment between the photographing optical system and the examinee's eye every time. Thus, photographed picture images would be in disagreement. And even if a photographing apparatus of a same type is used, photographed picture images would be in disagreement according to the respective adjustment condition of the apparatus.
In order to solve the above disagreement between picture images, the adjustment of the photographing apparatus and the alignment operation would take a long time and, if a special alignment device is added to the conventional photographing apparatus, the price will increase greatly. In film photography, in particular, disagreement of picture image could be found out only after development of the photographed film. Thereby it is necessary to photograph the examinee's eye again for the analysis of image of the eye.